For the future, it is envisioned that local networks will be called upon to serve from thousands to hundreds of thousands of resource-poor clients. These networks might be intra-building, intra-organization or even intra-city. Customizable and nevertheless extremely high performing servers will be required. These servers will heavily rely on caching. The hit server/miss server architecture described in the aforementioned co-pending patent application entitled "A Powerful And Flexible Server Architecture" is one example. The server architectures need basic cache-coherency mechanisms that permit efficient and simple implementation of application-specific cache-coherency and cache-replacement policies, preferably on a per item basis.
A huge variety of cache-coherency and cache-replacement policies is known, including the MESI (Modified, Exclusive, Shared, Invalid) protocol, which is mostly used for hardware cache memories, and lazy release consistency, which is mostly used for distributed-shared-memory systems implemented by software.
What is needed is a set of general basic mechanisms that enable one to implement virtually any (known or new) cache-coherency and/or cache-replacement policy. The basic mechanisms can be implemented by software, by hardware, or by a combination of both.